A transceiver node (e.g., a satellite) of a wireless communication system is used to transmit information to communication units (e.g., mobile subscriber units), receive information from communication units, and route information to remote destination devices through other transceiver nodes. Where multiple communication units are serviced by a single transceiver node, traditional multiple access techniques isolate signals from each communication unit by providing each unit with a unique disjoint frequency or time slot. These techniques include Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA), respectively. Multiple access can also be provided through sharing of a common spectrum, where allocation of disjoint frequency or time resources to each user is not attempted. Using the technique of spectrum sharing, or Code Division Multiple Access (CDMA), all bandwidth resources are allocated to all simultaneous users. Each user employs a noise-like but deterministic wideband signal occupying the entire frequency allocation.
Common to all of the above multiple access techniques is the limitation that data packets within a multiple access signal must be isolated by intermediate transceiver nodes between a transmitting unit and a destination transceiver node (i.e., a node which ultimately delivers the signal to a destination device). The signals must be isolated so that routing information associated with each data packet can be evaluated, and the packet can be routed by a "routing transponder" or "node" to the destination node or another intermediate node accordingly.
The data packet isolation method depends on the type of multiple access technique employed. For example, in a system employing TDMA, each intermediate transceiver node must extract each data packet from the time slot to which it is assigned, evaluate the routing data, determine the destination transceiver node based on the data, repack the data packet into a signal in another appropriate time slot, and then route the signal toward the destination node.
The evaluation and routing functions performed by the node, referred to herein as "onboard processing" increase proportionally with the number of active communication units supported by the node. Consequently, the service capacity of a node depends on the amount of hardware and software resources available to onboard processing tasks. Substantially higher capacities would likely result in higher costs and greater size and/or weight of the intermediate node (e.g., higher satellite costs and weight).
What is needed is a method and apparatus to substantially reduce onboard processing performed by transceiver nodes. Further needed is a method and apparatus for rapidly routing data through a communication system. Further needed is a method and apparatus for rapidly routing data contained within CDMA signals.